When draining used oil from an internal combustion engine or transmission pan the usual procedure is to unscrew the threaded plug received within the threaded pan opening and upon removal of the plug the oil drains from the pan.
This procedure, particularly when practiced by the home mechanic, often results in the oil running down the arm of the mechanic upon plug removal, and often the threaded plug is dropped into the waste oil receptacle requiring plug recovery and resulting in soiled hands. The problems created with the changing of engine oil by the home mechanic are well known to those who prefer to change their own engine oil without obtaining professional services.
It is known to utilize a valved oil pan drain plug wherein a portion of the plug remains within the pan threaded hole, and a valve element is associated with the pan attached plug portion to permit oil drainage without complete removal of the valve from the pan attached portion. An example of such a proposed device is shown in U.S. Pat. No. 3,727,638. However, commercially available valved oil pan plugs are difficult to install, the valve may be inadvertently loosened, and, previously, such devices have not been readily available.
It is an object of the invention to provide an oil pan drain plug of the valved type which is of economical construction, easy to install, and minimizes the likelihood of inadvertent loosening of the plug body from the pan when operating the valve.
A further object of the invention is to provide an oil pan drain plug of the valved type wherein the valve is rotated relative to a body threaded into the pan oil plug drain opening and flow through the plug is prevented by a threaded valve operated by a wrench, drainage through the plug occurring upon relatively limited rotation of the valve to the body.
Yet another object of the invention is to provide a two-part oil drain plug including a body and a valve threaded therein, the body being affixed to the pan drain opening, and the valve being positionable between open and closed positions upon rotation of the valve relative to the body.
An additional object of the invention is to provide a pan drain plug threaded into the pan drain opening wherein the plug includes self-tapping thread means to permit attachment of the plug to an opening having worn or damaged threads.
In the practice of the invention a body having a threaded inner end region is threaded into the threaded pan drain opening of an internal combustion engine oil pan, a transmission pan or the like. The body includes an axial bore which is threaded adjacent the body outer end region and a conical valve seat is located in the central region of the bore. Externally, the body is provided with wrench flats adjacent the exterior threads defined on the inner end region, and the body is provided with a cylindrical exterior surface adjacent the outer end region and such exterior surface has an axial dimension greater than the axial dimension of the body wrench flats.
A valve is threaded into the open-ended bore of the body and includes a stem defining a cylindrical wall and the innermost end of the stem is provided with a conical seal surface adapted to engage and seal against the body valve seat. The valve is provided with a coaxial bore intersecting the valve outer end, and inlet ports defined in the inner region of the valve bore establish communication between the valve bore and the stem wall adjacent the valve seal surface. At its outer exterior end, the valve is provided with wrench flats which, when the valve is rotated to engage the seal surface with the body valve seat, the valve wrench flats will be disposed adjacent the body outer end. The axial dimension of the wrench flats is less than the axial dimension of the body cylindrical outer end region.
While the configuration and dimensions of the body and valve wrench flats may be identical, the axial spacing between the wrench flats due to the presence of the body outer cylindrical end region surface minimizes the likelihood of a wrench being applied to the valve wrench flats also engaging the body wrench flats, and the construction of the invention substantially eliminates the possibility of inadvertent unloosening of the body from the pan threaded opening during operation of the valve.
As the body and valve of the plug of the invention may be readily manufactured on automatic screw machines, and as, preferably, the diametrical dimension of the wrench flats of the body and valve are identical in order to minimize the need for different sizes of raw stock, a drain valve in accord with the invention may be economically manufactured, assembled and packaged.